1. Technical Field
The present invention relates to a backup method of a microcomputer used in the case of stoppage of operation, a backup unit of the microcomputer, and a control unit for controlling a power window for automobile use.
2. Related Art
Recently, electronic control conducted by microcomputers has come into wide use in the field of general industrial equipment. Especially, electronic control has made remarkable progress for controlling automobiles synthetically and for controlling mobile communication devices. On the other hand, the microcomputer is disadvantageous in that it is affected by electromagnetic waves and further it tends to be damaged when it is covered with water according to rain or flood.
For example, a power window device for automatically opening and closing a windshield glass of an automobile door (hereinafter, such a windshield glass is referred to as xe2x80x9ca windowpanexe2x80x9d in this specification) by a motor is not an exception. When a failure is caused in the microcomputer in the above circumstances, various unpredictable problems may be caused.
Therefore, the following techniques have been proposed, by which the microcomputer is backed up in the power window device so that the safety of operation can be ensured in the case of failure of the microcomputer.
A backup device of the conventional power window device is operated as follows. When operation of the microcomputer is stopped because it is covered with water or some problems caused in the microcomputer, operation of a watchdog timer is stopped and impedance of the reset output of the watchdog timer is made high. Due to the foregoing, the microcomputer is stopped from being reset.
The reason why impedance of the reset output of the watchdog timer is made high when the microcomputer is covered with water or some problems caused in the microcomputer is described below.
Unless the reset of the microcomputer is stopped when the microcomputer is covered with water or some problems caused in the microcomputer, the reset output of the watchdog timer periodically repeats High/Low. Therefore, it can not be used as a condition of driving the backup circuit by which the windowpane can be manually pulled up and down.
Only when the reset output of the watchdog timer is at a low level, that is, only when the microcomputer is reset, the backup circuit can pull up and down the windowpane by manual operation. Therefore, when the reset output periodically repeats High/Low, it is impossible to pull up and down the windowpane in the practical use.
In this connection, the above conventional backup device has the following problems to be solved. The problems are described below.
Even when the microcomputer runs away temporarily which is not a case in which the microcomputer is covered with water or the microcomputer is out of order, impedance of the reset output of the watchdog timer becomes high. Therefore, when the microcomputer runs away even once, it is impossible to return the microcomputer to the state of normal operation, and the windowpane is pulled up and down only by the backup operation of the backup device, that is, the windowpane is pulled up and down only by the manual operation.
In a control system in which electric power supply to the power window unit is stopped when an ignition key is turned off, it is possible to return the microcomputer to the state of normal operation by turning on and off the ignition key. However, in a control system in which electric power is directly supplied from the battery, it is impossible to reset the microcomputer unless the battery is disconnected from the system.
Accordingly, when consideration is given to the practicality after the power window device has been incorporated into an actual automobile, it is desired that the fail-safe control, which corresponds to both the stoppage of operation caused by a temporary runaway of the microcomputer and the stoppage of operation caused by submergence, is performed by judging whether the power window device is in the stoppage of operation caused by a temporary runaway of the microcomputer or the stoppage of operation caused by submergence. That is, when the microcomputer is submerged and its operation is completely stopped, it is necessary that the motor drive which is a power source of opening and closing the windowpane is not stopped, but it is necessary that the motor drive control is conducted according to a state in which the switch of opening and closing the windowpane of each door of the automobile body is turned on so that the windowpane can be pulled up (closed) or the motor drive control is conducted according to a state in which the switch of opening and closing the windowpane of each door of the automobile body is turned on so that the windowpane can be pulled down (opened).
Accordingly, it is an object of the present invention to provide a backup method of a microcomputer used in the case of stoppage of operation. A backup unit of the microcomputer, and a control unit for controlling a power window for automobile use capable of conducting the most appropriate backup on an object to be controlled by the microcomputer in both cases of the stoppage of operation caused by a temporary runaway of the microcomputer and the stoppage of operation caused by submergence.
In order to accomplish the above object, the invention described in claim 1 provides a backup method of a microcomputer used in the case of stoppage of operation including the step of operating a backup means for conducting control to be conducted by the microcomputer when a pulse signal outputted from the microcomputer is stopped for a period of time exceeding a predetermined period of time.
According to the present invention, when operation of the microcomputer is completely stopped because the microcomputer is covered with water or the microcomputer is out of order, the backup means is operated at the point of time when operation of the microcomputer is completely stopped. Due to the foregoing, even if operation of the microcomputer is completely stopped in the middle of controlling an object to be controlled (for example, in the middle of controlling the motor which is a power source of opening and closing the windowpane), in exchange for the microcomputer, the backup means conducts controlling on the object to be controlled in exchange for the microcomputer. Therefore, even when operation of the microcomputer is completely stopped because the microcomputer is covered with water or the microcomputer is out of order, the object to be controlled by the microcomputer can be normally controlled.
The invention provides a backup method of a microcomputer used in the case of stoppage of operation in which the microcomputer is periodically reset when a frequency of a pulse signal outputted from the microcomputer becomes out of a predetermined range, the backup method including the step of operating a backup means for conducting control to be conducted by the microcomputer when the pulse signal outputted from the microcomputer is stopped for a period of time exceeding a predetermined period of time.
According to the present invention, when the microcomputer temporarily runs away in the middle of controlling an object to be controlled by the microcomputer, the microcomputer is reset. When operation of the microcomputer is completely stopped because the microcomputer is covered with water or the microcomputer is out of order, the backup means is operated at the point of time when the microcomputer is stopped.
Accordingly, the most appropriate backup can be conducted on the object to be controlled by the microcomputer in both the case in which operation of the microcomputer is stopped because the microcomputer temporarily runs away and the case in which operation of the microcomputer is completely stopped because the microcomputer is covered with water or the microcomputer is out of order.
The predetermined period of time is longer than a period of time from a temporary runaway of the microcomputer to a return to the normal state of the microcomputer.
The invention provides a backup unit of a microcomputer including: a backup means for conducting control to be conducted by the microcomputer in exchange for the microcomputer; an external microcomputer monitoring means, arranged outside the microcomputer, capable of conducting an enable/disable setting from the outside of the microcomputer, for monitoring a frequency of a pulse signal outputted from the microcomputer and resetting the microcomputer periodically when the frequency of the pulse signal becomes out of a predetermined frequency range; and an internal microcomputer monitoring means, incorporated into the microcomputer body as a program, for monitoring a pulse signal outputted from the microcomputer, for outputting a signal to disable the external monitoring means when the pulse signal is not outputted exceeding a predetermined period of time, and for making the backup means continue the operation while the external microcomputer monitoring means is being disabled.
According to the present invention, an external microcomputer monitoring means monitors a pulse signal outputted from the microcomputer and periodically conducts resetting on the microcomputer when the frequency of the pulse signal becomes out of a predetermined frequency range. The internal microcomputer monitoring means, incorporated into the microcomputer body, for monitoring a pulse signal outputted from the microcomputer, outputs a signal to disable the external monitoring means when the pulse signal is not outputted exceeding a predetermined period of time. The internal microcomputer monitoring means makes the backup means continue the operation while the external microcomputer monitoring means is being disabled. Due to the foregoing, for example, when operation of the microcomputer is completely stopped in the middle of controlling an object to be controlled by the microcomputer, the backup means controls the object to be controlled in exchange for the microcomputer. Therefore, even when operation of the microcomputer is completely stopped because it is covered with water or it is out of order, the object to be controlled by the microcomputer can be normally controlled.
Accordingly, the most appropriate backup can be conducted on the object to be controlled by the microcomputer in both the case in which operation of the microcomputer is stopped because the microcomputer temporarily runs away and the case in which operation of the microcomputer is completely stopped because the microcomputer is covered with water or the microcomputer is out of order.
The invention provides a power window control unit for automobile use including: a microcomputer for pulling up or down a windowpane according to the state of operation of an operation switch, the microcomputer outputting a pulse signal outside simultaneously with the start of operation; a backup means for conducting control to be conducted by the microcomputer in exchange for the microcomputer; an external microcomputer monitoring means, arranged outside the microcomputer, capable of conducting an enable/disable setting from the outside of the microcomputer, for monitoring a frequency of a pulse signal outputted from the microcomputer and resetting the microcomputer periodically when the frequency of the pulse signal becomes out of a predetermined frequency range; and an internal microcomputer monitoring means, incorporated into the microcomputer body as a program, for monitoring a pulse signal outputted from the microcomputer, for outputting a signal to disable the external monitoring means when the pulse signal is not outputted exceeding a predetermined period of time, and for making the backup means continue the operation while the external microcomputer monitoring means is being disabled.
According to the present invention, the external microcomputer monitoring means monitors a frequency of a pulse signal outputted from the microcomputer and resetting the microcomputer periodically when the frequency of the pulse signal becomes out of a predetermined frequency range. The internal microcomputer monitoring means, incorporated into the microcomputer body, for monitoring a pulse signal outputted from the microcomputer, outputs a signal to disable the external monitoring means when the pulse signal is not outputted exceeding a predetermined period of time. The internal microcomputer monitoring means makes the backup means continue the operation while the external microcomputer monitoring means is being disabled. Due to the foregoing, for example, when operation of the microcomputer is completely stopped in the middle of controlling an object to be controlled by the microcomputer, the backup means controls the object to be controlled in exchange for the microcomputer. Therefore, even when operation of the microcomputer is completely stopped because it is covered with water or it is out of order, the object to be controlled by the microcomputer can be normally controlled.
Accordingly, the most appropriate backup can be conducted on the object to be controlled by the microcomputer in both the case in which operation of the microcomputer is stopped because the microcomputer temporarily runs away and the case in which operation of the microcomputer is completely stopped because the microcomputer is covered with water or the microcomputer is out of order.
The internal microcomputer monitoring means outputs a signal to disable the external microcomputer monitoring means when the pulse signal outputted from the microcomputer is not outputted exceeding a period of time from a temporary runaway of the microcomputer to a return of the microcomputer to the normal state.